A heat treatment apparatus which performs a heat treatment on a plural sheets of substrates held by a holding unit while flowing an inert gas upward from below into a vertical processing container with a heating unit installed therearound, has been known. This heat treatment apparatus includes: a gas supply system which is installed in a lower end portion of the processing container to supply an inert gas; a gas supply header unit installed to flow the inert gas in a circumference direction of the processing container; and a gas introduction unit installed in the gas supply header unit to supply the inert gas into the processing container.
In this configuration, since the gas supply header is installed along an outer circumferential wall of the heated processing container, the introduced inert gas may be supplied into the processing container, while being heated. When the inert gas is introduced at a level of normal temperature, a cold spot is generated. This condenses a vaporized gas containing a photosensitizing agent included in a photoresist which is applied onto a surface of a substrate, thus causing a phenomenon in which a powder or liquid deposit adheres to a lower portion of the processing container. The conventional heat treatment apparatus suppresses the adhesion of the deposit to the lower portion of the processing container.
In addition, the vaporized gas which is obtained when moisture, solvent or the like included in the photoresist is vaporized during a heat treatment, is carried together with the inert gas when the inert gas introduced from the gas supply header unit flows upward from below within the processing container. Subsequently, the vaporized gas reaches a ceiling portion of the processing container, followed by being discharged to the outside through an exhaust pipe installed to communicate with an upper portion of the processing container.
However, although the conventional heat treatment apparatus suppresses the deposit from adhering to the lower portion of the processing container while the processing container is being heated, it fails to suppress the deposit from being generated while the processing container is not heated after the processing is terminated.
In particular, recently, it is sometimes the case that, from the viewpoint of improving productivity, a cooling process is applied to initiate a subsequent heat treatment after the termination of the current heat treatment in a short period of time, without waiting for a natural cooling of the heat treatment apparatus. To do this, the cooling process uses a cooling unit to positively cooling down the processing container by an air cooling from the surrounding of the processing container. In the cooling process, an exhaust gas generated from the processing container is condensed within an exhaust pipe due to residual heat obtained when the heat treatment is terminated or after the heat treatment is terminated, so that the condensate adheres to the interior of the exhaust pipe.